The use of support energy in the meat processing industry
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J. Sci. Fd Agric. 1978,29, 172-181
The Use of Support Energy in the Meat Processing Industry
J. Keith Jacques and Kenneth L. Blaxter*
Department of Management Science and Technology Studies, University of Stirling, Stirling, Scotland, and *The Rowett Research Institute, Bucksburn, Aberdeen, Scotland
(Manuscript received 22 August 1977)
A study of the consumption of support energy in the meat industry in Scotland involved both large meat factories and high street butchers. The energy cost of transport of live animals from farms to abattoirs was 0.5 x lo9 J/ton deboned meat for both pigs and cattle. Factory slaughtering, butchery and processing costs were 60 x lo9 J/ton deboned meat for pigs and 41 x 109 J/ton for cattle. When on-farm costs are included the support energy subsidy/ton meat was similar for both species at 110 x lo9 J/ton deboned meat. The energy subsidy incurred in meat factories/ton deboned meat varied with the extent of processing, from 27 x lo9 J/ton forjointed pork to 86 x l o 9 J for beef pies containing 34% meat. The imparting of convenience to food was achieved by expending additional labour and support energy in the ratio 4 x lo9 J/man hour. Separate calculations showed that maintenance of hygiene and disposal of effluent accounted for over half the total energy cost of factory operations.
Several analyses have been made to ascertain the total consumption of energy involved in the production, processing and distribution of food. Steinhart and Steinhartl showed that in the USA in 1970, the overall inputs were 2.2 x l0l8 J in the farm sector, 3.5 x 1018 J in catering industries and the home. Industrial use of energy in food processing is clearly a large proportion of the total. In the United Kingdom Leach2 has estimated that the inputs of energy for food production, pro- cessing, delivery and final preparation in the home are about 34 x l o 9 J per person per year and that food processing and wholesale and retail distribution accounts for over a third of the total.
Such studies and those of others (notably Hirst3 in the USA and Gifford and Millington4 in Australia) deal with the whole system of food provision, including the growing of crops and animals. Few studies have been made of individual items of food, although Leach2 has analysed in detail the support energy required to the point of retail sale to produce a loaf of bread and, using the UK Input-Output Tables,5 has estimated the support energy required by major sectors of the food and drink industries of the UK. The present study was undertaken to assess, in as direct a way as possible, the support energy required to produce meat and meat-containing foods. The investigation included detailed estimation of support energy required to transport live animals from farm to abattoir, to slaughter, process them, and to package, warehouse and deliver the final products to the retailer.
The investigation was carried out in the NE and E of Scotland, where almost 50 of Scottish meat production is located. Cattle and pig meat production were studied in the premises of three major meat processing firms and in five private butchers shops. The latter were selected at random in the Falkirk-Stirling area and two of them, besides selling manufactured meat products which they purchased wholesale, also prepared small quantities of sausages and pies. All butchers prepared
0022-5142/78/0200-0172 $02.00 0 1978 Society of Chemical Industry 172
Support energy in meat processing industry 173
considerable amounts of mince. All firms involved in the study provided information freely and it was on the basis of analysis of their records, supplemented by additional measurements where necessary, that estimates of energy consumption were made. Many difficulties arose, however, with respect to precise allocation of energy costs to particular products because of the complexity of the overall operations. Thus, certain initial costs, such as those of transport, lairage and slaughtering, had to be distributed over a number of final food products-fresh meat, edible fats, sausages, pies and other products. Distribution of energy costs equally applied to effluent disposal and provision of staff amenity. In addition, a trade in parts of carcasses which related to seasonal demands for particular manufactured products created additional distribution and summation problems. The conventions adopted to deal with these difficulties are given below.
The allocations of initial energy costs to final products were made in proportion to the mass of the animal component in the final product. The energy required to render technical fats, to manu- facture bone meal and to deal with blood was counted as a slaughter cost and was not separately assigned to these by-products. Since skins were often sold fresh, no energy was allowed for any subsequent transport or tanning of them. In these various ways the major part of the by-product costs was allocated to the final food product. In our opinion this approach is sensible because the primary process involved is the production of food and it is necessarily associated with the secon- dary processes of by-product disposal. Effluent costs were allocated in proportion to water use in the various parts of the overall processing, while the energy costs of provision of hygienic facilities (where they could not be allocated to a part of the process), laundry, cleaning, canteen and admin- istrative costs, were allocated in proportion to the manpower employed in each defined sector. For the energy cost of hygiene, however, dirty tasks such as slaughtering, butchering and bone meal manufacture were charged at a rate per caput which was three times that charged for the cleaner operations which, from observation, required smaller quantities of hot water and steam. Where a firm purchased a carcass or side from elsewhere to augment the production of a particular product, the assumption was made that the support energy expended up to the point of purchase was the same as that which would have been incurred had the meat been processed within the plant.
These conventions are peculiar to the meat industry and obviously have some effect on the final estimates, but are not thought to be of major dimension. Other conventions were adopted in the estimation of energy costs of particular items and are listed below.
2.1. Direct consumption of fuel and power Input energies per unit of fuel derived from the studies of Leach and Slesser6 and were taken to be 14.7 x 106 J/kW h for electricity, 138 x lo6 J/Therm for gas and 187.3 x 106 J/gal for both heavy and light fuel oil. In many instances individual electrically powered machines in a department of a factory were not separately metered. To estimate power consumption the fraction of total plant operating time during which the machine was switched in was multiplied by the power rating of the machine. No allowance was made for any effects on consumption of start up or shut down. Direct tests using power meters of this method of assessment showed it to be accurate to & 5 %.
2.2. Energy cost of replacement of capital equipment Following the practice adopted by Blaxter? a value of 136 x lo6 J /Ll capital depreciated at 1974 values was used to cover the cost of replacement of plant and machinery.
2.3. Energy cost of packaging materials purchased Most of the purchased inputs of packaging consisted of low density polythene and polypropylene for vacuum packing and shrink wrapping of meat, trays of foamed polystyrene far sausage packing and aluminium trays for pies. Nylon reinforced sachets were used for large catering packs and joints. In addition, composite aluminium-polythene laminates were used in decorative packs, while card- board boxes were employed in bulk packaging. The weights of materials per final package were determined and the energy costs per ton of packaging material were those listed by Berry and Makino.8 These are known to be applicable in the United Kingdom.
174 J. I(. Jacques and I(. L. Blaxter
2.4. Energy cost of transport The information made available by the firms allowed energy costs of transport to be estimated directly from vehicle life, fuel consumption and cost of tyres. Component factors have been listed9 in terms of cost.
2.5. Energy cost of non-meat additions to products Sausage and pie formulations are proprietary secrets. A pork pie contains flour and rusk ingredients, while a Cornish pasty also contains carrclts and other root vegetables. The support energy cost of production of these items has been given a representative value in Table 2 in the column referring to final product, but this support energy has been omitted from the column referring to the energy per unit of deboned meat in pies and other products in which meat is but one ingredient.
Total support energy for baked bread and pastry products (including energy to grow the wheat grain) has been taken at 1 1 x lo9 J per ton; ex farm gate figures for (raw) vegetables lie generally between 1 and 3 x loy J per ton (UK) (M. Green, personal communication) and the slightly pessi- mistic figure of 3 x lo9 J per ton has been used in this work. In the case of calculations based on deboned meat, the energy associated with cooking pies and pasties is attributed to the meat on a simple proportional basis.
2.6. Energy cost of labour The energy required to support the personal and domestic life of factory or shop workers is not considered. Energy expended in canteen facilities in larger factories is, however, included as well E S those facilities concerned with hygiene within the factory. The convention to ignore the energy required by labour for personal support is that used by Blaxter7 but not by Leach2 in energy accounting studies.
2.7. Calculation and expression of results The whole complex process of manufacture of products was separated into stages which coincided with divisions of the factory or shop, and energy costs incurred at earlier stages were allocated in proportion to quantities of meat entering the next stage. Results are finally expressed per ton of saleable product. In addition, results are calculated per ton of meat; this requires careful definition of the term meat and we distinguish between meat defined as dressed carcass weight and deboned meat with surplus fat removed and with edible offal added back as appropriate.
Table 1 gives the factors which have been used in this work to convert live animal units to carcass or deboned meat. For pies, sausages and bacon/ham products, the calculation initially evaluated the support energy per ton of product first; for these products the energy inputs per animal were calculated back using the factors in Table 1 . The converse applied to basic butchery operations.
In deriving Table 1, the following conventions were employed: for cattle, the dressed carcass was taken to be 55% of live weight. The meat yield from the carcass, combined with edible offals, referred to in Table 3 as deboned meat was taken to be 41 % of the live weight. Edible fat from the carcass and offals was assessed as 5.2% and industrial fats as 4.1 of live weight. Total bone
Table 1. Number of animals required to produce 1 ton of carcass or deboned meat
Factors to convert to:
1 tonof Live 1 ton of deboned
animal carcasses meat
Pigs 1 .o 1 8 . 6 22.2 Cattle 1 .o 3 .5 4 . 7
Support energy in meat processing industry 175
and hoof was estimated to be 13 %, 7.7 % deriving from the dressed carcass and 5.3 % from the non-carcass component. For pigs, the dressed carcass with head included was taken to be 73 % of live weight. Edible offal was assumed to account for 5 % and bone for 14% of the dressed carcass. The edible meat content, including edible offal, thus represents 56% of the live weight (excluding the head). This somewhat arbitrary choice of values, based on anatomical and butchery evidence, formed the basis for all derived calculations.
The data are presented firstly in operational terms, summarising the energy costs involved in each stage of the process. They are then recombined on a flow basis to give the energy costs of the final products. Transport of animals to the abattoir is dealt with first, then the processing costs, and lastly the transport of meat and meat products and the support energy costs incurred at the retail outlet.
3.1. Transport of animals to abattoirs The energy cost of transport of an animal to the point of slaughter is the product of energy cost per vehicle mile and length of the journey (including any unladen running) divided by the number or mass of animals transported per journey. Running and depreciation costs for the fairly standard 3-axle 12-16 ton gross laden weight vehicle, consuming fuel oil at the rate of 12 mpg and with a capital value of E l 0 000 and an amortisation life of 5 years, were computed from factory records. Analysis of day-by-day delivery notes provided estimates of distances travelled and number of animals transported. The results are given in Table 2.
Table 2. Energy cost of transporting live animals to the point of slaughter: large abattoirs
Energy (J x lo6) consumed per mile
Average one-way distance transported Per ton Average energy per animal delivered
Animal (miles) Per animal live weight to factory from farm (J x lo9)
40 1.38 2 .6 25 0.30 3.3
They show that energy costs/ton-mile were 2.6-3.3 x lo6 J (1.62.1 x lo6 Jitonne-km). These are lower than the figure of 4.0 x lo6 J/ton mile calculated by Leach* from data of the UK Transport and Road Research Laboratoryg with an arbitrary correction of 25 % for depreciation, tyres and repairs (one-way distance) as used by Blaxter.? The lower value largely reflects the considerable efficiency of transport organisation in terms of avoidance of part loads exerted by the firms studied. Expressed per ton of deboned meat entering the factory (see Table 7), the energy cost per ton of animal transported expressed as deboned meat was the same for pigs and cattle at 0.5 x lo9 J/ton.
3.2. Meat factory operations In factories which produce a number of different products, operations follow a logical sequence and this dictates departmentalisation of the enterprise. The initial analysis was based on these departments and Table 3 summarises the operations involved and the energy costs incurred in each. From this primary information the energy inputs into the final products were computed with the results given in Table 4. In this table all by-product energy costs are assigned to the final products.
The magnitude of the support energy required may be placed in perspective by considering that the heat of combustion of muscle tissue devoid of fat is approximately 5.4 x log J/tonne. The support energy required to manufacture and package sliced bacon is thus about eight times the heat of